The purpose of the RFA for a Sickle Cell Disease (SCO) Clinical Research Network (CRN) is to establish an infrastructure with 15 clinical centers that will design and perform multi-center therapeutic trials to improve health outcomes in persons with sickle cell disease. Clinical investigators from the Emory and Morehouse Schools of Medicine propose to establish one of the 15 clinical centers in Atlanta. The proposal includes three elements: The Clinical Research Core will contribute to the design and implementation of SCO CRN studies, and enroll subjects at Children's Healthcare of Atlanta and the Grady Health System. Project 1 will test the hypothesis that losartan, an angiotensin receptor antagonist, will reduce the rate of progression of renal disease in patients with sickle nephropathy. The hypothesis will be tested in two groups: patients with macroalbuminuria and overt nephropathy, and patients with microalbuminuria. In addition to determining the effect on progressive renal disease, the study will compare the safety and tolerability of losartan vs. placebo when administered long-term in albuminuric patients with sickle cell nephropathy. Project 2 is a prospective phase III randomized trial to test the hypothesis that nalbuphine is superior to morphine in the treatment of vaso-occlusive pain in SCO because patients will suffer fewer episodes of acute chest syndrome and will suffer fewer side effects because of less respiratory suppression and reduced release of histamine. A second hypothesis is that high-dose PCA with low-dose infusion of analgesic is superior to low-dose PCA with high-dose infusion. The hypothesis will be tested by a four-arm study that will compare morphine to nalbuphine and low-dose constinuous infusion with high-dose PCA to high-dose infusion with low-dose PCA for each analgesic. The work of the CRN will contribute importantly to lessening morbidity and mortality from complications of SCO. Two two proposed projects will improve treatment of pain, the most common and disabling manifestation of SCO and lessen the impact of chronic kidney disease.